The present invention relates in general to a magnetic head system for tape players of the auto-reverse type, and in particular to such a system capable of automatically change tracks of the magnetic tape by rotation of the magnetic head both in recording and reproduction.
In the prior art, various attempts have been made to develop tape players capable of playing multi-track magnetic tape players continuously from track to track by automatically shifting into the next track at the end of travel of each track. In some examples such as eight-track endless reproduction systems and four-channel recording and reproduction systems the magnetic tape is switched from one track to the next while being run along the head only in one direction. Other types of apparatus are characterized by two-way (forward and reverse directions) drive of the tape both for recording and reproduction operation, in which change of the tracks may be effected in one of the following three main methods: (1) The method by which the multi-track magnetic tape is played by a magnetic head assembly comprising operational heads corresponding in number to the tape tracks. (2) The method by which the multi-track magnetic tape is played by a single magnetic head having an operational tape-playing tracks arranged across its front core gap corresponding in number to the tape tracks. The required track is picked up by line connection in the magnetic head core circuit. (3) The method by which the multi-track magnetic tape is played by a movable magnetic head having operational tape-playing tracks arranged across the front core gap relatively less in number than the tape tracks, which magnetic head is designed to be shifted traversely across the tape face to pick up the required track.
Neither of the above mentioned methods, however, has been found acceptable for use with tape players of the type in which the magnetic tape is run in both forward and reverse directions for operation, particularly in view of their inability to provide for proper azimuth adjustment required for optimum recording and reproduction. In addition, method (1) has been found to suffer from several drawbacks. First, the number of magnetic heads required to meet the number of the tape has led to an increase of manufacturing cost. Secondly, because of the increased surface area of the tape face in contact with the tape playing surface of the multi-head unit, undesirably great reaction forces tend to act on the tape face in the opposite direction to that of travel of the tape, with the resulting tendency of developing wow and flutter. Head systems utilizing the principle of method (2), on the other hand tend to cause cross-talk between adjacent tracks in recording and reproduction operation because of the limited narrow band width of the individual tracks. Method (3) poses difficulties in obtaining mechanical precision to insure correct positioning of the head into the track at change of tracks.
In order to eliminate the above mentioned disadvantages a rotatable magnetic head system, such as the one illustrated in FIG. 1A to FIG. 1C, has been developed which comprises a single magnetic head capable of playing the magnetic tape continuously from track to track both in recording and reproduction. In operation, the tracks of the magnetic tape are traversed by rotation of the magnetic head about its axis. A magnetic head system similar to the one shown in FIGS. 1A to 1C can be applied in tape players of the cassette type, and usually comprises a magnetic head 10 including a magnetic core designed for application to two-track (two-channel) magnetic tapes, a supporting arm 2 to support the magnetic head at its one end, a rotating shaft 4 rotatively disposed and axially affixed at its one end to the other end of the supporting arm for rotation thereof, and a gear wheel 5 concentrically made integral with the rotating shaft 4 and operatively connected to a suitable drive means (not shown) such as a motor-driven gear system which is in mesh engagement with the gear wheel 5. A rotating arm 3 is fixedly retained to the supporting arm 2 in such a manner to extend perpendicular to the axis of the rotating shaft 4, so that the rotating arm 3 rotates with the gear wheel. The magnetic head has at least two tape-playing surfaces, or magnetic core front gaps, substantially 180.degree. spaced apart from each other along its circumference. With this arrangement, when the first track of the magnetic tape, in operation, has reached its end on one of the tape-playing surfaces, the drive means automatically acts to rotate through the rotating shaft 4 the magnetic head 10 so as to bring the other tape-playing surface in contact with the next track of the tape which is simultaneously to proceed in the opposite direction. In this manner, continuous recording and reproduction can be obtained. The rotating shaft 4 is rotatively disposed on a support frame 6 that is secured on a conventional head slide plate (not shown). The support frame is provided at opposide end with a pair of azimuth adjusting screws 7a and 7b with the interposition of springs. These two azimuth adjusting screws 7a and 7b extend through the support frame to abut against the rotating arm 3 to thereby prevent it from rotation beyond restrictive rotational points determined by the lower end of the screws. The azimuth adjusting screws 7a and 7b can be rotated in either direction to change the position of the restrictive rotational points to obtain the optimum azimuth angle, or contact angle of the magnetic head with respect to the face of the tape loaded. The two azimuth adjusting screws are intended for adjustment in forward and reverse tape drive, respectively.
In this manner, the rotatable magnetic head system can perform automatic change of tracks while at the same time changing the direction of travel of the tape from the forward to reverse track with the rotation of the magnetic head about its axis through an angle of 180.degree.. These prior art rotatable magnetic head systems have been found advantageous in many respects. For example, it is well known that they have found successful application in tape players of the cassette type having tape drive systems in which the magnetic tape is driven in both directions, forward and reverse. In addition, these magnetic head systems are known to be able to operate efficiently with stereo magnetic heads as well.
However, there conventional magnetic head systems of the rotatable head type, while adequate in operation, have some mechanical problems, mainly because of their characteristic structural design; the magnetic head in the supporting arm being rotated between tape playing positions to change tracks of the magnetic tape to be played by a gear wheel that is mounted on the substantially same rotatable shaft as the head supporting arm is carried. Since the principal components of the magnetic head system of this type are usually arranged in tandem, one after another, the distance l from the magnetic head to the gear wheel for directly rotating the head tends to increase. This stands against the present-day trend of the general adoption towards the smaller design such as represented by small-size and thin-cabinet compact type cassette decks.